Chemical reactions

Science

The substance was broken into smaller pieces.

Which **two** are signs that a chemical reaction has taken place?

A substance changes from a gas to a liquid. This is a {{}} change.

carbon dioxide + water → propane + oxygen

carbon dioxide + water = propane + oxygen

propane + oxygen → carbon dioxide + water

propane + oxygen = carbon dioxide + water

Select the correct word equation for the following reaction: propane and oxygen react together to produce carbon dioxide and water.

the number of atoms of each element must be equal on both sides.

the number of atoms of each element must be higher in the products than the reactants.

the number of atoms of each element must be lower in the products than the reactants.

magnesium carbonate → magnesium oxide + carbon dioxide

copper oxide + zinc → zinc oxide + copper

Match the type of chemical reaction to the equation.

What is the balanced symbol equation for copper + oxygen → copper oxide?

When chocolate changes from a solid to a liquid, it is called {{}}.

What is the process called when water changes from a liquid to a gas?

A substance made from hydrogen and chlorine.

A substance made from sodium, carbon and oxygen.

A substance made from iron, sulfur and oxygen.

Match the compounds to their descriptions.

If a compound contains three elements and one is oxygen, the name ends in …

How can you tell when an egg is cooking in a frying pan?

Which of the following is a chemical reaction?